Semiannual oscillation,annual oscillation,quasibiennial oscillation,and solar cycle variation of the OH airglow emission in the mesopause region

The vertically integrated emission rate,centroid altitude,peak emission rate,and peak height of the hydroxyl(OH)airglow were calculated from Thermosphere Ionosphere Mesosphere Energetics and Dynamics(TIMED)/Sounding of the Atmosphere using Broadband Emission Radiometry(SABER)observations to study the seasonal and interannual variations in the intensity and location of the OH emission.The emission rate is inversely proportional to the height of the emission,with the semiannual oscillation dominating at low latitudes and the annual oscillation dominating at higher latitudes.The OH emission is modulated by the quasibiennial oscillation at the equator,and the quasibiennial oscillation signal is weak at other latitudes.We represented the vertical transport of atomic oxygen by using atomic oxygen concentrations obtained from a global atmospheric model,the Specified Dynamics Whole Atmosphere Community Climate Model with thermosphere and ionosphere eXtension simulations.Compared with the amplitudes of the migrating diurnal tide(DW1)calculated from temperature data observed by TIMED/SABER,we found that both the vertical transport of atomic oxygen and DW1 amplitudes in the equatorial region exhibit semiannual oscillation and quasibiennial oscillation,which have a strong correlation with the variations in the amplitude and phase of semiannual oscillation and quasibiennial oscillation in OH emission.It is likely that the DW1 affects the vertical transport of atomic oxygen that is involved in the reaction to produce O3,thus affecting the OH emission.We analyzed the relationship between OH emission and solar activity by using the solar radio flux at 10.7 cm as a proxy for solar activity.The results showed that the OH emission is well correlated with solar activity,and the modulation of OH emission by solar activity has a significant latitudinal variation.The small correlation between emission height and solar activity indicates that solar activity modulates OH emission mainly through chemical rather than dynamic processes.

A new strategy for ionospheric remote sensing using the 130.4/135.6 nm airglow intensity ratios

We demonstrate here that global-scale determination of a key ionospheric parameter,the peak height of the F_(2)region(h_(m)F_(2)),can be obtained by making a simple ratio measurement of the atomic oxygen 130.4 and 135.6 nm emissions in the far-ultraviolet nightglow with a nadir-viewing system such as a pair of photometers suitable for flight on a CubeSat.We further demonstrate that measurements from an altitude that is within the typical range of nighttime h_(m)F_(2)250−450 km can provide the ratios that are needed for retrieval of the h_(m)F_(2).Our study is conducted mostly through numerical simulations by using radiative transfer models of the two emissions coupled with empirical models of the atmosphere and ionosphere.Modeling results show that the relationship between the h_(m)F_(2)and the intensity ratio is sensitive to the altitude from which the emissions are observed,primarily because of the distinctly different degrees of resonant scattering of the two emissions in the atmosphere.A roughly quadratic relationship can be established for observations from an orbit of~400 km,which enables h_(m)F_(2)retrieval.Parametric analysis indicates that the relationship can be affected by the ambient atmospheric conditions through resonant scattering and O2 absorption.For typical nighttime conditions with h_(m)F_(2)250−450 km,retrieval of the h_(m)F_(2)from synthetic observations shows that the typical errors are only a few kilometers(up to~20 km),depending on the accuracy of the ambient conditions predicted by the empirical models.Our findings pave the way for use of the 130.4/135.6 nm intensity ratios for global-scale monitoring of the nighttime ionosphere at mid to low latitudes.

Airglow observation by Fabry-Perot Interferometer

An all-sky and a scanning Fabry-Perot interferometers (FPI) have been developed for observations of vertical winds and two-dimensional atmospheric motions in the low-thermosphere and the mesosphere region by the measurement of Doppler shift and broadening of airglow emission lines. The system of FPI is described and the method of data analysis is proposed, an example of observation is also given.

A simulation study of 630 nm and 557.7 nm airglow variations due to dissociative recombination and thermal electrons by high-power HF heating

One of the important effects of the ionospheric modification by high-power waves is the airglow enhancement. Both the thermal electrons and the dissociation recombination contribute to generate the airglow emissions during HF heating. However, the relative importance of the airglow emission induced by dissociative recombination and thermal electrons has been rarely investigated. In this study, we carry out a simulation study on the airglow produced by high-power HF heating at nighttime associated with dissociative recombination and thermal electrons. SAMI2(Sami2 is Another Model of the Ionosphere) is employed to simulate the ionospheric variations during the HF heating. The main conclusions from this study are as follows:(1) For the airglow induced by dissociative recombination, both 630.0 nm and 557.7 nm emissions show a decrease at the heating wave reflection height during the heating period,while when the heating is turned off, an increase is shown at lower altitudes. The reduction of airglow during the heating is caused by the rapid increase of electron temperature and the diffusion of plasmas dominates the after-heating airglow enhancement.(2) 630.0 nm emission due to thermal electrons is greatly enhanced at the wave reflection height, indicating that thermal electrons play a major role in exciting 630.0 nm emission. For the 557.7 nm emission, the excitation threshold(4.17 e V) is too high for thermal electrons.(3) The combined effect of dissociative recombination and thermal electrons could be the possible reason for the observed X-mode(extraordinary mode) suppression of 630.0 nm airglow during O-mode(ordinary mode) enhancement.

Long-Term Changes in Night Time Airglow Emission at 557.7 nm over Mid Latitude Japanese Station i.e., Kiso (35.79oN, 137.63oE)

The present study describes the long-term changes in Pre-midnight and Midnight airglow intensities of 557.7 nm during the period 1979-1994 over mid latitude Japanese station i.e., Kiso, Tokyo Astronomical Observatory, University of Tokyo (35.79oN, 137.63oE;1130 m), Japan. It has observed that there is a positive increasing decadal change in Midnight and Pre-midnight mesospheric airglow intensity of the range 25 - 88 R. This range is the order of 10 to 30% of the observed MARV and average night airglow intensity of 250 R. Besides this long-term trend, inter-annual monthly variation is also seen from fluctuation of yearly variation of deviation values from MARV to particular average monthly values. The present observations about the positive decadal change in night time mesospheric airglow intensity has been further linked to the reduction of mesospheric electron densities and temperature or shrinking and cooling of the lower ionosphere as established from the long-term behavior of mesospheric parameters such as a negative decadal change in thermal structure, electron density, neutral density parameters as per studies reported by other researchers.

A Method of Inversing the Peak Density of Atomic Oxygen Vertical Distribution in the MLT Region From the OI (557.7 nm)Night Airglow Intensity

In this paper, using the MSISE-90 model as the reference atmosphere, we discuss the feasibility and method of deducing the peak densities of the undisturbed atomic oxygen profiles in the MLT region (the mesosphere and lower thermosphere region) from OI (557.7 nm) night airglow intersities. The peak densities for different seasons, latitudes and longitudes are deduced from OI (557.7nm) airglow intensities through this expression. We analyze the features of inversion relative errors and discuss the influence of the variations in temperature on inversion errors. The results indicate that all inversion errors are less than 5% except for those at high altitudes in the summer hemisphere. And the impact of the variations in temperature on errors is not significant.

The Nonlinear Model of the Response of Airglow to Gravity Waves

In this paper, we develope a timodependent, nonlinear, photochemical-dynamical 2-D model which is composed of 3 models: dynamical gravity wave model, middle atmospheric photochemical model, and airglow layer photochemical model. We use the model to study the effect of the gravity wave propagation on the airglow layer. The comparison between the effects of the different wavelength gravity wave on the airglow emission distributions is made. When the vertical wavelength of the gravity wave is close to or is shorter than the thickness of the airglow layer, the gravity wave can make complex structure of the airglow layer, such as the double and multi-peak structures of the airglow layer. However, the gravity wave that has long vertical wavelength can make large scale perturbation of the airglow emission distribution.

High-precision temperature retrieval algorithm and verification for mesospheric airglow spectrum photometer

Photometric technology,characterized by its compact structure and relatively high stability,finds wide application in measuring airglow spectra.This instrumentation is anticipated to assume a pivotal role as the primary equipment for extensive network observations of middle and upper atmospheric temperatures in China,thereby providing crucial support for space environmental monitoring and atmospheric dynamic research.Nevertheless,susceptibility to various factors such as instrument inconsistency,variability in observation conditions,and alterations in the background atmospheric environment across different stations poses a challenge,potentially resulting in data inconsistencies in network observations.In response to these challenges,we propose a multiple-parameter iterative inversion(MPII)algorithm for temperature retrieval based on a mesospheric airglow spectrum photometer(MASP)developed by our research group.This algorithm accurately identifies the center of the image circle,corrects image distortion,and thereby obtains an accurate synthetic spectrum reflective of actual observations.It encompasses five adjustable parameters:sky background light,atmospheric temperature,filter temperature,optical system focal length,and degree of synthetic spectrum modulation.Compared to traditional methods,significant enhancements in the accuracy of the inverted temperature are achieved.To validate the effectiveness of the MPII algorithm,we conducted combined active and passive remote sensing synchronous measurements using MASP in conjunction with a sodium fluorescence Doppler lidar developed by the National Space Science Center.By utilizing the lidar temperature as a reference,atmospheric background radiation is mitigated from the MASP data,and the temperature is inverted using the MPII algorithm.Comparative analysis with the traditional method reveals that temperatures calculated by the MPII algorithm exhibit better consistency than those observed by the lidar.

A statistical analysis of conjugate equatorial plasma bubbles based on 630 nm airglow observations

Using the observations of the 630-nm all-sky imagers(ASIs)located in the geomagnetic conjugate points in the American sector from 2014 to 2017,this study statistically analyzed the features of conjugate equatorial plasma bubbles(EPBs),including their occurrence rate,zonal width,location and zonal drift velocity.The results show that the occurrence rate of the EPBs that occur simultaneously at geomagnetic conjugate points is~84%.The zonal widths of the EPBs are mainly~100 km,and the width differences of EPBs between the northern and southern hemispheres are mainly within±30 km.The zonal displacements of the center locations of the northern and southern EPBs are within±50 km.The zonal drift velocities of the northern and southern EPBs are nearly equal.However,it should be noted that the velocity of the EPBs in the northern hemisphere is 10%faster than that in the southern hemisphere.The results suggest that conjugate EPBs are common.Moreover,the non-conjugate EPBs in the northern and southern hemisphere can occur occasionally,which is probably associated with the different ionospheric backgrounds between the two hemispheres.The features of the conjugate EPBs as shown in this study provides support for the nowcasting of EPBs in the conjugate hemispheres.

GBAVTII探测西安上空夜气辉反演O_(2)(0-1)柱浓度及其波动的研究

探测高层大气的粒子浓度具有重要的科学意义.本文利用安装在中国西安城区(海拔457m, 34.23°N,109.01°E)的自制地基气辉成像干涉仪GBAVTII(Ground-based atmosphere VER&temperature imaging interferometer)对峰值高度在94 km处的867.7 nm O_(2)(0-1)夜气辉长期定点观测,反演得到O_(2)(0-1)的柱浓度,并根据大气温度及O_(2)(0-1)粒子柱浓度的扰动提取得到大气重力波、行星波周期.本文首先阐述了地基GBAVTII探测气辉的原理,并从气辉辐射理论及地基探测模式导出气辉强度表达式,建立地基仪器探测得到的气辉的积分体发射率IER(Integrated Emission Rate)与大气中O_(2)(0-1)柱浓度的关系,然后利用2019年以来的多日观测数据,得到西安地区上空O_(2)(0-1)粒子的柱浓度量级为10~4cm^(-2);经对比发现2020年9月17日GBAVTII探测O_(2)(0-1)柱浓度结果与NRLMSISE-00模型数据的相对误差在0.5%~30%.我们从GBAVTII整夜拍摄气辉成像干涉图中反演出西安上空90~100 km的大气温度和O_(2)(0-1)柱浓度及扰动特征,得到周期在8~10 h左右的潮汐波,去掉潮汐趋势的温度和柱浓度残差序列,利用小波分析提取得到周期为2.3 h的重力波.最后我们利用2022年4月21日—2022年5月6日期间的O_(2)(0-1)柱浓度探测序列得到日平均柱浓度并提取准2日的行星波周期.GBAVTII所探测得到大气波动的周期尺度与其他已有中纬度地区的探测结果相吻合.

临近空间大气风场温度场卫星遥感技术研究综述

研究临近空间的风场和温度场对大气圈层之间的动量及能量传输、大气成分的输运以及大气环流的非线性突变有重要的科学意义,然而此区域的大气风温数据稀缺是国际亟待解决的难题之一。卫星遥感技术是获取大气风温信息的重要手段,然而受工程难度的限制,目前国际上针对临近空间风温遥感的卫星载荷十分有限。首先,概述了国际上具有代表性的大气风温卫星遥感载荷的发展现状。然后,系统性地综述了针对临近空间区域的近红外、长波红外和中波红外三类典型的风温遥感技术的研究进展;包括各观测目标源的光谱特性、载荷仪器的研制进展、以及风温探测能力;并讨论了各技术方案的优劣性。最后,对多种技术方案进行了对比汇总,为后续临近空间探测技术提供了参考和启示。展望未来临近空间星载风温遥感技术的发展趋势,着眼于风温遥感载荷的空间覆盖能力、时间连续性及探测精度、同时讨论载荷研制的工程难度,为临近空间风温遥感卫星研发和应用提供有效思路。

1.27 μm O_(2)(a^(1)Δ g)气辉临边观测辐射传 输特性

1.27μm波段的O_(2)(a^(1)Δg)气辉辐射具有辐射信号强、空间跨度大、自吸收效应弱等诸多内禀优势,是临近空间大气遥感的重要目标源,对于中高层大气的动力学及热学特性研究,全球温室气体探测,以及臭氧浓度三维层析等卫星遥感具有重要的科学意义和应用价值。首先基于O_(2)(a^(1)Δg)光化学反应模型,研究了O_(2)(a^(1)Δg)气辉的产生机制及湮灭机理,在此基础上,计算得到了O_(2)(a^(1)Δg)气辉体辐射率廓线,并基于HITRAN数据库给出的谱线强度及爱因斯坦系数,提出了两种计算O_(2)(a^(1)Δg)气辉光谱分布的方法。采用最新的分子光谱参数、光化学反应速率常数及F10.7太阳紫外通量等参数,结合光化学反应模型计算得到的O_(2)(a^(1)Δg)气辉体辐射率廓线信息,借助逐线积分算法,建立了1.27μm O_(2)(a^(1)Δg)气辉临边观测辐射传输理论模型,并分析了自吸收效应对不同临边观测高度处气辉辐射光谱强度的影响。然后,利用剥洋葱算法,对大气图像扫描成像吸收光谱仪(SCIAMACHY)在临边观测模式下测得的O_(2)分子近红外大气带的气辉辐射信号进行处理得到了目标层O_(2)(a^(1)Δg)气辉辐射光谱,并通过谱积分算法反演得到了O_(2)(a^(1)Δg)气辉的体辐射率廓线信息。最后通过对比气辉临边观测辐射传输理论模型计算得到的以及SCIAMACHY仪器测量反演得到的1.27μm O_(2)(a^(1)Δg)辐射光谱及体辐射率廓线信息,验证1.27μm O_(2)(a^(1)Δg)气辉临边观测辐射传输理论模型的可靠性与合理性。基于比对结果,对O_(2)(a^(1)Δg)气辉临边辐射强度和体辐射率的影响因素进行了分析。分析结果表明,在50 km以上的高空区域,理论计算结果与卫星实测结果吻合性较好,而随着海拔高度的降低,两者的偏差逐渐增大,这是因为在临边观测模式下,中低空区域的卫星遥感信号受自吸收效应及大气散射效应影响严重。此外,与HITRAN数据库给出的谱线强度参数相比,基于爱因斯坦系数建立的O_(2)(a^(1)Δg)气辉临边辐射模型与卫星实测结果更加吻合。1.27μm O_(2)(a^(1)Δg)气辉临边观测辐射传输理论模型的建立,对于临近空间大气遥感,奠定了理论基础。

Measurement of Martian atmospheric winds by the O_(2) 1.27 μm airglow observations using Doppler Michelson Interferometry: A concept study

China’s Mars exploration mission has stimulated tremendous interest in planetary science exploration recently.To propose potential scientific research projects,this study presents a concept simulation for the measurement of Martian atmospheric winds using the Doppler Michelson interferometry technique.The simulation is based on the satellite instrument initially designed for the Dynamic Atmosphere Mars Observer(DYNAMO)project to measure vertical profiles of winds from the 1.27μm airglow observations in the Martian atmosphere.A comprehensive DYNAMO measurement simulation forward model based on an orbit submodel,an atmospheric background field submodel,and an instrument submodel is developed using the Michelson equation.The simulated interferogram signal over the field of view(FOV)calculated by the forward model is associated with the filter transmittance function,column emission rate of airglow,wind velocity,temperature,and the Michelson phase.The agreement between the derived atmospheric signals from the simulated interferogram without altitude inversion and the input parameters used to initiate the forward model confirms the validity of the forward model.

基于O_(2)分子1.27μm气辉反演临近空间温度廓线的新方法

1.27μm波段O_(2)(a^(1)Δg)气辉的辐射强度高、自吸收效应弱,是反演临近空间大气温度的理想目标源。基于O_(2)分子气辉光谱理论以及“剥洋葱”算法,利用扫描成像大气吸收光谱仪(SCIAMACHY)的近红外临边观测数据,成功反演50~100 km区域的大气温度廓线。与SABER、ACE-FTS及激光雷达的观测结果对比表明,在55~85 km的切线高度范围内温度测量误差优于±10 K,而在55 km以下与85 km以上空间区域,由于受到自吸收效应、大气散射以及OH气辉的光谱污染等干扰,温度反演结果出现显著偏差。

Airglow simulation based on the Atmospheric Ultraviolet Radiance Integrated Code of 2012

The Atmospheric Ultraviolet Radiance Integrated Code(AURIC) is a software package developed by Computational Physics, Inc.(CPI) under the sponsorship of the Air Force Phillips Laboratory/Geophysics Directorate(PL/GP)(currently the Air Force Research Laboratory) for middle and upper atmospheric radiance modeling from the far ultraviolet to the near infrared. The AURIC has been considered as a general model for the radiative transfer simulation of airglow. Based on the theory of MODerate resolution atmospheric TRANsmission(MODTRAN), the AURIC extends calculation to altitudes above 100 km and the wavelength down to 80 nm. A package of AURIC v1.2 was released in 2002, which can be used for single-point simulation from 1947 to 1999. It means that the model is not suitable for atmospheric simulation of large datasets or for atmospheric parameters retrieval from amount of satellite measurements. In this paper, AURIC v1.2 is upgraded to AURIC-2012 based on MATLAB with improvements for modules of the Geomagnetic Parameter(GEOPARM), Atmosphere neutral composition(ATOMS), and Ionospheric electron density(IONOS). The improved AURIC can be used for global automatic airglow simulation and also for automatic retrieval of atmospheric compositions from satellite global observations, such as O/N2 and electron density etc. Besides, the model supplies possibilities for further improvement of airglow radiative mechanism and for substitution of other modules. Based on the AURIC-2012, Limb Column Emission Intensity(L-CEI) and Volume Emission Rate(VER) are calculated. For validation, the results were compared with measurements of the Global Ultraviolet Imager(GUVI) and TIMED Doppler Interferometer(TIDI), respectively. The averaged relative errors of L-CEI and VER at peak altitude are both within 20%. Finally, L-CEI varying with latitude, altitude, solar activity, and geomagnetic activity is simulated, and the distribution characteristics of the simulation and their influencing factors are analyzed subsequently.

磁暴期间OI 135.6 nm气辉经纬及高度分布的变化特征

利用GUVI探测器观测的OI 135.6 nm气辉辐射数据,研究了2003年10月和11月两次持续时间不同的强磁暴期间气辉辐射强度经纬度分布及纬度–高度分布的变化。结果表明,全球大部分区域内OI 135.6 nm气辉辐射强度在磁暴期间会随着Dst指数的降低而增强,与磁暴的剧烈程度呈现准正相关关系。从纬度上看,气辉辐射强度的增强会由磁静期的磁赤道两侧附近向高纬地区延伸至南北半球50°附近,增幅基本在80%以上,最大可超过200%,且经纬度分布在磁暴期间的变化情况呈现出南北不对称性和纬向不对称性;从高度上看,气辉辐射强度的增强会由磁静期的300~400 km(即电离层F2层高度)扩散至其他高度,特别是在100~200 km(即低热层高度)的部分纬度上会出现相比其他高度更为显著的增强,增幅超过300%;气辉辐射出现增强的时间与磁暴相位基本同步。

利用OI135.6nm夜气辉辐射探测电离层峰值电子密度及电子总含量的研究

测量夜间135.6nm大气气辉辐射强度是目前有效的电离层探测方式之一,我国即将在风云三号卫星上搭载仪器,利用该波段夜气辉辐射测量来反演电子总含量(本文所指电子总含量表示卫星高度以下大气柱的电子含量)及峰值电子密度,因此非常有必要开展相关的气辉发光模型及反演研究.在介绍氧原子135.6nm波段夜气辉激发机制基础上,考虑辐射在传输过程中受到大气氧原子的散射及氧气分子的吸收,采用迭代法求解包含多次散射及大气吸收衰减的辐射传输方程,得到该波段的体发射率,最终通过考虑包含辐射传输的路径积分计算得到135.6nm气辉辐射强度值.对结果的分析表明:该气辉模型能较好地描述体发射率随高度的分布特征,计算得到的135.6nm夜气辉辐射强度在不同时空及太阳活动的分布与相应条件下峰值电子密度(NmF2)及电子总含量(TEC)的分布基本一致.相同的时空及太阳活动输入条件下,模式计算的135.6nm夜气辉辐射强度与国外同类模式结果的值平均偏差约为3%.文中最后介绍了通过135.6nm夜气辉的辐射强度探测来反演电离层峰值电子密度NmF2及电子总含量TEC的反演方法.

高层大气测风用地基F-P干涉仪的数值模拟

热层大气风场、温度场对热层-电离层耦合研究、热层环流特性研究以及太阳活动和地磁活动研究等有着重要意义,同时其也是航天器飞行环境预报的重要物理基础.目前,由于热层所处位置较高,大气非常稀薄,风场探测难度较大,因此针对热层大气风场的探测手段非常少.Fabry-Perot(FP)光学干涉仪可通过观测气辉来进行风场探测,其对成像系统像质要求不高,在设计中无需过分追求像质,已经成为热层风场测量的重要工具.由于风场观测气辉的辐射强度非常微弱,因此必须进行FP干涉仪测量系统优化,获得相对较强的辐射强度,以提高风场测量精度.但目前,对FP干涉仪系统优化方面的研究较少,且在测风误差评价方面的工作也不充实.本文通过热层测风用固定间距标准具地基FP干涉仪数值模型的建立,解决FP干涉仪设计过程中各参量的优化问题,并提出一种新的测风误差估算方法.数值模型结果分析表明,在目前探测器观测技术水平下,采用全部干涉环参与计算并结合像元合并技术进行风速反演可最大限度地提高测量精度.此外,由于气辉辐射强度是影响热层大气风场测量精度的重要因素,因此在仪器测风精度性能评价时需确定观测对象强度,即气辉的辐射强度.

星载远紫外极光/气辉探测发展综述

地球热层和电离层是近地卫星运行的主要场所,也是空间天气对人类活动影响的重要区域.气辉和极光是高层大气中的重要发光现象,其辐射特性、特别是紫外波段的辐射特性,是高层大气和电离层物理化学过程信息的重要来源.本文详细分析了国外远紫外极光/气辉探测和相应探测器的发展里程,并结合我国相关研制技术和水平,提出了发展星载极光/气辉探测的基本考虑和建议.

基于多台站OH全天空气辉成像仪观测的中国中纬地区重力波传播特性

利用位于中国中纬地区6个OH气辉成像仪2012年1月至2013年12月两年的观测数据,我们研究分析了重力波传播特征.结果表明重力波的水平波长、观测周期和水平相速度分别主要分布于10-35km,4-12min和30-100m·s-1范围.夏季,重力波主要沿极向方向传播.然而,冬季,他们有向赤道方向和平行于赤道方向的传播趋势.同时,我们结合TRMM卫星和ECMWF数据,发现在夏季重力波的北向传播趋势可能主要由观测台站南方的对流活动导致.然而,对流层顶附近的急流可能在冬季重力波的主要传播方向方面做出较大贡献.分析结果也表明,低层-中层大气背景风的滤波效应仅在夏季与中国中纬地区重力波纬向传播方向各向异性吻合较好.